1. Field of the Invention
The present invention relates to a multi-stage-extension zoom lens barrel assembly.
2. Description of the Related Art
Three-stage-extension zoom lens barrel assemblies are known as a common lens barrel structure for use in conventional zoom lenses of compact cameras. One type of such conventional three-stage-extension zoom lens barrel assemblies includes a fixed barrel secured to a camera body and two lens barrels retained within the fixed barrel. The fixed barrel and one of the two barrels that is directly inside the fixed barrel are connected to each other via helicoids whereas the other of the two barrels that is placed inside the first barrel is connected to the first barrel via a cam structure. Alternatively, some multi-stage-extension zoom lens barrel assemblies use a helicoid structure in all of the connections between lens barrels to move the connected lens barrels relative to one another.
Although the lens barrel assemblies employing a cam structure use fewer parts and thus are small, these barrel assemblies tend to have a low rigidity since relative movement between the lens barrel and the barrel with cam grooves is carried out via the cam grooves. Furthermore, such barrel assemblies must be completely disassembled when it is necessary to replace parts for maintenance or when it is desired to replace scratched parts. In contrast, the multi-stage-extension zoom lens barrel assemblies that use a helicoid structure in all of the connections between the barrels have a high rigidity due to the nature of the helicoid structure. These assemblies can be readily assembled or disassembled, making maintenance easy. However, the structure of these barrel assemblies requires at least one additional lens barrel, which means the outermost barrel (i.e., the barrel with the largest diameter which is closest to the camera body) has a larger diameter.
In view of the above problems associated with conventional multi-stage-extension zoom lens barrel assemblies, a multi-stage-extension zoom lens barrel assembly is provided, which can be readily assembled and ensures easy maintenance while maintaining the overall rigidity of the barrel assembly, without making the construction large.
For example, a multi-stage-extension zoom lens barrel assembly is provided, having a helicoid structure for allowing movement of a lens barrel in an optical axis direction, the helicoid structure including a first inner peripheral helicoid ring having a first helicoid formed on the outer periphery thereof and an outer peripheral helicoid ring having a second helicoid formed on an inner periphery thereof for engaging with the first helicoid, the multi-stage-extension zoom lens barrel assembly including a first linear guide ring provided in the first inner peripheral helicoid ring so that the first linear guide ring is relatively rotatable and integrally movable in the optical axis direction together with the first inner peripheral helicoid ring; and a first outer barrel for externally covering the first linear guide ring, the first outer barrel and the first inner peripheral helicoid ring being formed separately from each other, the first outer barrel being supported on the first linear guide ring so as to relatively rotate and move in the optical axis direction together with the first linear guide ring, wherein the first outer barrel is detachably attached to the first inner peripheral helicoid ring, the first outer barrel being integrally rotatable about the optical axis and integrally movable along the optical axis with the first inner peripheral helicoid ring.
The outer peripheral helicoid ring can include a fixed barrel secured to a camera body, the second helicoid formed on the inner periphery of the fixed barrel engaging with the first helicoid formed on the outer periphery of the first inner peripheral helicoid ring, so that the first inner peripheral helicoid ring advances and retreats when the first inner peripheral helicoid ring is rotated. The first linear guide ring, guided by the fixed barrel so as to move along the optical axis without rotating with respect to the fixed barrel, can advance and retreat together with the first inner peripheral helicoid ring without rotating as the first inner peripheral helicoid ring advances and retreats while the first inner peripheral helicoid ring rotates.
It is desirable for the first outer barrel and the first linear guide ring to be connected to each other via slidable engagement of a key formed on one of the first outer barrel and the first linear guide ring with a circumferential groove formed on the other of the first outer barrel and the first linear guide ring so as to allow the first outer barrel and the first linear guide ring to rotate relative to each other and move together along the optical axis, the circumferential groove and the key being arranged so as to be engaged with, and disengaged from, each other via relative movement thereof along the optical axis when the multi-stage-extension zoom lens barrel assembly has extended by a predetermined amount past a limit of a normal-use range.
The first linear guide ring can include a third helicoid on an inner periphery thereof, the first linear guide ring including a second inner peripheral helicoid ring including a fourth helicoid on an outer periphery thereof for engaging with the third helicoid; a second linear guide ring, which is provided within the second inner peripheral helicoid ring, so that the second linear guide ring can advance and retreat along the optical axis with respect to the first linear guide ring and relatively rotate with respect to the second inner peripheral helicoid ring and to integrally move together with the second inner peripheral helicoid ring along the optical axis; and a second outer barrel, which is provided between the first linear guide ring and the second linear guide ring so as to allow the second outer barrel to relatively rotate with respect to the second linear guide ring and to integrally move together with the second linear guide ring along the optical axis, the second outer barrel being connected to the second inner peripheral helicoid ring so as to integrally rotate together with the second inner peripheral helicoid ring.
The first linear guide ring further can include a first guide slot formed along the third helicoid extending therebetween; wherein a first guide head is detachably attached to the outer periphery of the second inner peripheral helicoid ring, the first guide head being placed through the first guide slot and engaging a first head guide groove formed on the inner periphery of the first outer barrel, the first guide head rotating together with the first outer barrel and relatively movable with respect to the first outer barrel along the optical axis.
The second linear guide ring can further include a third outer barrel having a fifth helicoid on a rear outer periphery thereof for engaging with a sixth helicoid provided in the inner periphery of the second linear guide ring; and a third linear guide ring provided within the third outer barrel so as to allow the third linear guide ring to relatively rotate with respect to the third outer barrel and to integrally move together with the third outer barrel along the optical axis, the third linear guide ring being guided to move along the optical axis with respect to the second linear guide ring. The third outer barrel further includes a second guide head detachably attached to the rear outer periphery thereof, the third outer barrel being guided along the optical axis by the second guide head placed through a second guide slot formed on the second linear guide ring along the sixth helicoid extending therebetween, the second guide head engaging with a linear guide slot formed on the inner periphery of the first outer barrel.
The second outer barrel and the second inner peripheral helicoid ring can be connected to each other via slidable engagement of a key formed on one of the second outer barrel and the second linear guide ring with a circumferential groove formed on the other of the second outer barrel and the second linear guide ring so as to allow the second outer barrel and the second linear guide ring to rotate relative to each other and move together along the optical axis, the circumferential groove and the key being arranged so as to be engaged with, and disengaged from, each other via relatively movement thereof along the optical axis when the multi-stage-extension zoom lens barrel assembly has extended by a predetermined amount past a limit of a normal-use range.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-82091 (filed on Mar. 22, 2001) which is expressly incorporated herein by reference in its entirety.